Laser–plasma acceleration1, 2 is an emerging technique for accelerating electrons to high energies over very short distances. The accelerated electron bunches have femtosecond duration3, 4, making them particularly relevant for applications such as ultrafast imaging5 or femtosecond X-ray generation6, 7. Current laser–plasma accelerators deliver 100 MeV (refs 8–10) to GeV (refs 11, 12) electrons using Joule-class laser systems that are relatively large in scale and have low repetition rates, with a few shots per second at best. Nevertheless, extending laser–plasma acceleration to higher repetition rates would be extremely useful for applications requiring lower electron energy. Here, we use single-cycle laser pulses to drive high-quality MeV relativistic electron beams, thereby enabling kHz operation and dramatic downsizing of the laser system. Numerical simulations indicate that the electron bunches are only ∼1 fs long. We anticipate that the advent of these kHz femtosecond relativistic electron sources will pave the way to applications with wide impact, such as ultrafast electron diffraction in materials13, 14 with an unprecedented sub-10 fs resolution15.
At a glance
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